Method of treating a petroleum fraction using selective solid adsorbents



June 23, 1959 H, v. HEss ETAL 2,891,902

METHOD oF TREATING A PETROLEUM FRAc'rIoN USING sELEcTrvE soun AnsoRBENTsFiled may 21; 1956 :s sheets-sheet 1 I H, v. HEss E-rAL 2,891,902 METHODOF TREATING A PETROLEUM FRACTION USING June 23,

A SELECTIVE SOLID ADsoRBENTs C5 Sheets-Sheet 2 Filed May 21, 1956 H. v.Hr-:ss Er AL `lune 23, '1959 2,891,902 METHOD 0F TREATING A PETROLEUMFEACTION USING SELECTIVE SOLID ADsoEBENTs Filed May 21, 1956 3Sheets-Sheet 3 United States Patent O IVIETHOD F TREATING A PETROLEUMFRAC- TION USING SELECTIVE SOLID ADSORBENTS Howard V. Hess, Glenham, andEdward R. Christensen, Beacon, N.Y., assignors to Texaco Inc., acorporation of Delaware Application May 21, 1956, serial No. 586,218

11 claims. (cl. 20s- 65) This invention relates to a method of treatinghydrocarbon fractions, such as petroleum fractions and hydrocarbonsynthesis (Fischer-Tropsch) fractions. In accordance with oneembodiment, this invention relates to the treatment of hydrocarbonfractions in the naphtha or gasoline boiling range, said fractionscontaining straight chain hydrocarbons and non-straight chainhydrocarbons, in order to improve their quality as a motor fuel. Inaccordance with still another embodiment, this invention relates to animproved hydrocarbon conversion process. This invention is primarilydirected to the upgrading of petroleum fractions containing straightchain hydrocarbons and non-straight chain hydrocarbons, especiallynaphtha stocks wherein the amount of straight chain hydrocarbons issubstantial, e.g., in the range 2-30% by volume and higher.

Accordingly, it is an object of this invention to pro- Vide an improvedprocess for treating hydrocarbon fractions containing straight chainhydrocarbons and non-straight chain hydrocarbons.

g It is another object of this invention to provide a flexiblehydrocarbon converting process which is capable of handling a widevariety of hydrocarbon fractions containing straight chain hydrocarbonsand non-straight chain hydrocarbons.

Still another object of this invention is to provide a combinationhydrocarbon treating process for treating hydrocarbon fractionscontaining straight chain hydrocarbons and non-straight chainhydrocarbons wherein the straight chain hydrocarbons are selectivelyadsorbed by means of a solid selective adsorbent, followed by desorptionof the straight chain hydrocarbons in a special manner in accordancewith this invention.

Still another object of this invention is to provide a combinationhydrocarbo-n treating process wherein a hydrocarbon fraction containingstraight chain hydrocarbons and non-straight chain hydrocarbons caneventually be converted substantially entirely to non-straight chainhydrocarbons.

Yet another object of this invention is to provide a combinationhydrocarbon treating process wherein a hydrocarbon fraction containingaromatic hydrocarbons, branched chain aliphatic hydrocarbons andstraight chain hydrocarbons is separated into each of these components.

In at least one embodiment of this invention at least one of theforegoing objects will be achieved.

How these and other objects of this invention are achieved will becomeapparent with reference to the accompanying disclosure and drawingwherein:

Fig. l schematically illustrates one embodiment of the practice of thisinvention employing a special desorption zone wherein regeneration andtransfer of the special selective adsorbent are simultaneously effected,and

Fig. 2 schematically illustrates an embodiment of the practice of thisinvention employing in combination a prefractionation operation,catalytic reforming, a subsequent distillation fractionation operation,an adsorption operation, a desorption operation and isomerization of2,891,902 Patented June 23, 1959 the resulting desorbate, all theaforementioned operations being carried out in combination to produce ablended hydrocarbon fuel especially suitable for use in spark ignitioninternal combustion engines, and

Fig. 3 schematically illustrates another embodiment of the practice ofthis invention employing in combination catalytic reforming, solventextraction, selective adsorption, all cooperating to produce separatehydrocarbon streams .containing substantially only aromatichydrocarbons, non-straight chain non-aromatic hydrocarbons and straightchain hydrocarbons.

In accordance with our invention We have provided an improved processfor treating or converting a hydrocarbon fraction containing straightchain hydrocarbons and non-straight chain hydrocarbons which comprisessubjecting a hydrocarbon fraction to be treated to contact with aselective adsorbent which selectively adsorbs straight chainhydrocarbons to the substantial exclusion of non-straight chainhydrocarbons to adsorb straight chain hydrocarbons from said fraction,separating from the aforesaid adsorption operation a resulting treatedefuent having a reduced straight chain hydrocarbon content and saidsolid selective adsorbent containing straight chain hydrocarbonstherein, and regenerating the resulting separated adsorbent within adesorption zone by contact with a gaseous desorbing medium wherein theadsorbed straight chain hydrocarbons are desorbed from the selectiveadsorbent and wherein simultaneously the selective adsorbent undergoingregeneration is swept along and entrained by the gaseous desorbingmedium to one other end of the desorption Zone where the resultingregenerated adsorbent is separated from the gaseous desorbing medium andthe resulting gaseous desorbed straight chain hydrocarbons. Followingthe abovementioned regeneration-desorption operation the resultingregenerated selective adsorbent is returned to contact additionalhydrocarbon feed containing straight chain hydrocarbons and non-straightchain hydrocarbons for the separation of straighe chain hydrocarbonstherefrom.

By straight chain hydrocarbon is meant aliphatic or acyclic or openchain hydrocarbon which does not possess side chain branching.Representative straight chain hydrocarbons are the normal parafins andthe normal oletns, monoor poly-olefins, including the straight chainacetylenic hydrocarbons. The non-straight chain hydrocarbons comprisethe aromatic and naphthenic hydrocarbons as well as the isoparanic andisoolenic hydrocarbons and the like. Straight chainhydrocarboncontaining mixtures which are suitably treated in accordancewith this invention include the various petroleum fractions, such as anaphtha fraction, a gasoline fraction and the like. Particularlysuitable for treatment in accordance with this invention are straightchain hydrocarbon-containing fractions having a boiling point or aboiling range in the range of l0-600 F. and higher and containing asubstantial amount of straight chain hydrocarbons, e.g., 2-35% by volumeand higher. More particularly, a petroleum fraction suitable for use inthe practice of this invention might have an initial boiling point inthe range 40-300 F. and an end point in the range 15G-600 F.Furthermore, a petroleum fraction suitable for use in the practice ofthis invention must contain both straight chain and non-straight chainhydrocarbons and might have the following composition:

Acyclic unsaturates (including normal olefins and isooleiins) 0-50 3Typical renery stocks or fractions which are applicable tothe practiceof this invention are a wide boiling straight run naphtha, a lightstraight run naphtha, a heavy straight run naphtha, a catalytic crackednaphtha, a thermally cracked or thermally reformed naphtha, a catalyticreformed naphtha and the like.

Any solid selective adsorbent which selectively adsorbs straight chainhydrocarbons to the substantial exclusion of non-straight chainhydrocarbons can be employed in the practice of this invention. It ispreferred, however, to employ as the selective adsorbent certain naturalor synthetic zeolites or alumino-silicates, such as a calciumalumino-silicate, or a sodium calcium alumino-silicate, which exhibitthe property of a molecular sieve, that is, matter made up of porouscrystals wherein the pores of the crystals are of molecular dimensionand are of substantially uniform size.

A particularly suitable solid adsorbent for straight chain hydrocarbonsis a calcium alumino-silicate, apparently actually a sodium calciumalumino-silicate manufactured by Linde Air Products Company anddesignated Linde Type A Molecular Sieve. The crystals of this particularcalcium alumino-silicate have a pore size or diameter of about 5Angstrom units, a pore size sufciently large to admit straight chainhydrocarbons, such as the normal paramns and normal olens, to thesubstantial exclusion of the non-straight chain naphthenic, aromatic,isoparaflinic and isoolefnic hydrocarbons. This particular selectiveadsorbent is available in various sizes such as l or 1/16 cylindricalpellets, microspheroids or as a finely divided powder having a particlesize in the range 0.5-5.0 microns, exhibiting a bulk density in lbs. percubic foot of 33, and a particle density in grams per cc. of 1.6.

Other suitable solid selective adsorbents include the synthetic andnatural zeolites which, when dehydrated, may be described as crystallinezeolites having a rigid three dimensional anionic network and havinginterstitial dimensions suiciently large to adsorb straight chainhydrocarbons but suiciently small to exclude non-straight chainhydrocarbons possessing larger molecular dimensions. The naturallyoccurring zeolite, chabazite, exhibits such desirable properties.Another suitable naturally occurring zeolite is analciteNaAlSi2O5-l-l20, which, when dehydrated, and when all or part of thesodium is replaced by an alkaline earth metal, such as calcium, by baseexchange yields a material which may be represented by the formula (Ca,Naz) Al2Si4O12-2l-l2() and which, after suitable conditioning, willadsorb straight chain hydrocarbons to the substantial exclusion ofnon-straight chain hydrocarbons. Naturally occurring or syntheticallyprepared phacolite, gmelinite, harmotome and the like or suitable baseexchange modifications of these zeolites are also suitable.

Other solid inorganic or mineral selective adsorbents are known and maybe employed in the practice of this invention. It is contemplated thatselective adsorbents having the property of selectively adsorbingstraight chain hydrocarbons to the substantial exclusion of non-straightchain hydrocarbons in the manner of a molecular sieve may be obtained bysuitable treatment of various oxide gels, especially metal oxide gels ofthe polyvalent amphoteric metal oxides.

Encapsulated solid selective adsorbents are particularly useful in thepractice of this invention. Encapsulated adsorbents wherein theselective adsorbent, such as a sodium calcium alumino-silicate (Linde 5AMolecular Sieve), which normally are friable and fragile materials, isencapsulated within a porous envelope, such as wire mesh or a porousceramic envelope or coating, are particularly useful in the practice ofthis invention. Suitable encapsulated adsorbents are disclosed in ourcopending patent application Serial No. 511,952, tiled May 3l, 1955, andin copending patent application Serial No. 511,949, led May 31, 1955, inthe name of Howard V. Hess, one

l of the coinventors of this invention. The disclosures of theabove-identiiied patent applications are herein incorporated and madepart of this disclosure.

The adsorptive separation of the straight chain hydrocarbons from thehydrocarbon fraction undergoing treatment is preferably carried out inthe gaseous phase and at any suitable temperature and pressure effectiveduring the adsorptive separation operation to maintain the hydrocarbonfraction undergoing treatment in the vapor phase. For example, theadsorptive separation of the straight chain hydrocarbons by the solidselective adsorbent can be carried out at a temperature in the range15G-900 F. and at any suitable pressure, such as a pressure in the range0-2000 p.s.i.g. and higher, the temperature and pressure being adjustedwith respect to the hydrocarbon fraction undergoing treatment tomaintain the hydrocarbon fraction in the vapor phase.

The regeneration of the selective adsorbent or the desorption of thestraight chain hydrocarbons contained adsorbed in the solid selectiveadsorbent can be made at any suitable temperature and pressure,preferably at a temperature and pressure such that the resultingdesorbed straight chain hydrocarbons are in the vapor phase.

For example, the regeneration-desorption operation may be carried out ata pressure in the range 0-2000 p.s.i.g. or less. Generally a desorptionpressure in the range 1075O p.s.i.g. is suitable. It is sometimesdesirable to carry out the desorption operation at a pressuresubstantially lower than the adsorption pressure. The pressure employedduring the adsorptive separation operation is not determinative of thedesorption pressure and any suitable desorption pressure may beemployed. Substantially the same comment may be made with respect to thedesorption temperature in the practice of this invention. lt is`sometimes desirable, however, to carry out subfstantially isothermaladsorption-desorption operations. Any suitable desorption temperature inthe range 300- 1100 F., higher or lower, may be employed. It ispreferred, however, to carry out the regeneration-desorption operationat an elevated temperature, such as a temperature in the range 40G-900F., or at a temperature at least about degrees Fahrenheit higher thanthe adsorption temperature, especially in an isobaricadsorption-desorption operation. It is realized, of course, that thedesorption temperature should not be excessively high, for example, notgreater than about 1100-1300" F. in the case of Linde Type 5A MolecularSieve, since such high temperatures would lead to the destruction of theadsorbent material, presumably by collapse of the crystal structure,with resultant loss of its selective adsorption properties.

Although it is possible to eiect desorption of the adsorbed straightchain hydrocarbons from the solid adsorbent by the application of heatalone, for example, by radiant heating, it is a feature of thisinvention that the desorption operation is carried out within adesorption zone in the presence of a gaseous desorbing rnedium wherebythe selective adsorbent undergoing desorption or regeneration issimultaneously selectively desorbed or relieved of the adsorbed straightchain hydrocarbons and carried along or entrained by the gaseousdesorbing medium.

As a general rule any suitable `gaseous desorbing medium may be employedin the practice of this invention. A suitable gaseous desorbing mediumis methane, ethane, propane, natural gas, hydrogen, flue gas, carbondioxide, carbon monoxide, nitrogen, high temperature superheated steam,or mixtures thereof. In general, any `gaseous or vaporized materialchemically inert with respect to the adsorbent and readily separable byfractionation, liquefaction, solvent extraction or adsorption and thelike from the desorbed straight chain hydrocarbons is suitable as thedesorbing medium in the practice of this invention. It is preferred,however, to employ as the gaseous desorbing medium a hydrogenontainingstream, such as the gaseous hydrogen-containing elfluent recovered froma catalytic reforming operation, e.g., the hydrogen-containing effluentfrom a Platformer. Also preferred as the gaseous dmorbing medium is a C4hydrocarbon fraction, eig., n-butane and/or isobutane and similarhydrocarbons, including their higher molecular weight homologs, C5 andhigher hydroarbons, which are readily separable as by distillation fromthe resulting desorbed straight chain hydrocarbons.

`Referring now to the drawing and in greater detail to Fig. 1 avaporized petroleum fraction or naphtha feed, such as a depentanizedlight catalytically reformed naphtha or a light straight run naphtha,having a boiling range in the range 75-250 F., is introduced intoadsorber 11 via line 12 wherein it countercurrently contacts adownwardly moving mass of solid selective adsorbent or freely fallingsolid selective adsorbent which selectively absorbs straight chainhydrocarbons to the substantial exclusion of non-straight chainhydrocarbons. The selective adsorbent enters adsorber 11 via star valve14, the amount and/ or rate of introduction of selective adsorbent intoadsorber 11 and the amount or rate of removal of selective adsorbentfrom adsorber 11 via star valve 15 being controlled to maintain adownwardly moving bed or mass of adsorbent or freely falling adsorbentas desired. Adsorber 11 is operated under suitable conditions oftemperature and pressure to effect adsorption of straight chainhydrocarbons from naphtha feed introduced thereinto with the result thatthere issues from the upper portion of adsorber 11 Via line 16 afinished naphtha substantially free of straight chain hydrocarbons orhaving a substantially reduced straight chain hydrocarbon content.

The adsorbent removed from adsorber 11 via star valve 15 enters conduitor transfer means 18 wherein it travels downwardly to the lower end oflift pipe 19. The adsorbent entering the lower end of lift pipe 19 issubstantially saturated with straight chain hydrocarbons. At the lowerend of lift pipe 19 the adsorbent is contacted with hot desorbing-liftgas introduced into the lower end of lift pipe 19 via line 20. Thetemperature of the desorbing-lift Igas thus introduced into lift pipe 19is such as to effect rapid desorption of the adsorbed straight chainhydrocarbons from the adsorbent, thereby regenerating the adsorbent.Further, the quantity and rate of introduction of the desorbing-lift gasintroduced into lift pipe 19 is such that the adsorbent is entrained inthe upward flowing desorbing-lift gas within lift pipe 19 andtransported to the upper end thereof. C3, C4, C5 and higher molecularweight hydrocarbons, e.g., normal butane and/or isobutane, areparticularly suitable as a desorbing-lift gas.

When the adsorbent is transported by the desorbinglift gas into theupper end of lift pipe 19 into enlarged section 21 thereof the velocityof the dcsorbing-lift gas therein is reduced with the result that theentrained adsorbent tends to drop out of the desorbing-lift gas. It ismentioned at this time that the entrainment or lifting of the adsorbentwithin lift pipe 19 is aided by the release of the desorbed straightchain hydrocarbons within lift pipe 19, thereby introducing a greaterquantity of gaseous materials within lift pipe 19 and leading to ahigher gas velocity which Yaids in entraining the adsorbent. Thedesorbing-lift gas as well as the resulting desorbed straight chainhydrocarbons are removed from enlarged section 21 at the upper end oflift pipe 19 via line 22. A baffle is provided within enlarged section21 of lift pipe 19 in order to `promote and facilitate the separation ofthe entrained adsorbent from the entraining streams of desorbing-liftgas and gaseous desorbed straight chain hydrocarbons. The resultingregenerated adsorbent now having a substantially reduced straight chainhydrocarbon content or substantially free of straight chain hydrocarbonsis removed from the enlarged section 21 and passed via conduit 25 tostar valve 14 through which it is controlledly introduced into adsorber11 to contact additional naphtha feed for the separation and removal ofstraight chain hydrocarbons therefrom.

Referring now to Fig. 2 of the drawing which schematically illustratesanother embodiment of the practice of this invention, a petroleumfraction containing straight chain hydrocarbons and non-straight chainhydrocarbons, such as a relatively wide boiling naphtha fraction, e.g.,a straight run naphtha having a boiling range in the range 60-450 F., isintroduced via line 30 into fractionator 31 from which there is removedoverhead via line 32 a depentanized light naphtha stream having aboiling range in the range 75-275" F. and from the lower portion offractionator 31 -via line 34 a heavy naphtha stream, such as a naphthastream having a boiling range in the range 20G-450 F.

The heavy naphtha stream in line 34 is introduced into catalyticreformer 3S wherein it undergoes catalytic reforming, involvingisomerization, dehydrogenation, aromatization or dehydrocyclization,disproportionation, all taking place more or less simultaneously.Catalytic reforming is -a well known operation as evidenced by the manycommercially available catalytic reforming processes, e.g., Platforming,Ultraforming, Powerforming, Houdriforming, Sovaforming, Catforming andthe like. Usually catalytic reforming processes employ an activedehydrogenating platinum-containing catalyst, which catalyst is alsoeffective as an isomerization and dehydrocyclization catalyst. Catalyticreforming is usually carried out at a relatively elevated temperature inthe range 700-l000 F., more or less, and at a relatively elevatedpressure in the range 50-900 p.s.i.g. in the presence of recyclehydrogen recovered from the resulting catalytic reformer eiiluent.

There issues from catalytic reformer 35 a catalytic reformate via line36 which is introduced into gas separator 38 from which there isseparated overhead via line 39 a gaseous stream containing a largeproportion of or substantially only hydrogen. The remaining reformatestream removed from separator 38 via line 40 is introduced intodebutanizer 41 from which there is removed overhead via line 42 anormally gaseous hydrocarbon stream containing C4 and lighterhydrocarbons. The remaining catalytic reformate is removed from thelower end of debutanizer 41 via line 44. If desired, a debutanizedreformate may be removed as product from line 44 via line 45.

In the preferred manner of operation in accordance with this inventionthe debutanized reformate from line 44 is introduced via line 46 intofractionator 47 where there is removed overhead via line 48 a lightreform-ate fraction, such as a depentanized light reformate fraction.The remaining heavy reformate fraction is recovered from the lower endof fractionator 47 via line 49.

The light reformate fraction in line 48 may be recycled in part, ifdesired, via lines 50 and 34 to catalytic reformer 35. The lightcatalytic reformate in line 48, however, is advantageously introducedvia line 32 into adsorber-desorber unit `51 in admixture with the lightnaphtha issuing from fractionator 31 via line 32. As indicated in Fig.2, if desired, a part of the light naphtha issuing from fractionator 31via line 32 may be introduced via lines 52, 50 and 34 to catalyticreformer 35 along with the light catalytic reformate removed fromfractionator 47 via line 48.

Within adsorber-desorber unit 51 the light naphtha and light catalyticreformate streams introduced thereinto are contacted with a suitablesolid selective adsorbent which selectively adsorbs straight chainhydrocarbons to the substantial exclusion of non-straight chainhydrocarbons so as to effect removal of the straight chain hydrocarbonstherefrom. Adsorber-desorber unit 51 may be operated in any suitablemanner, such as in the manner illustrated in Fig. 1 of the drawing,effective to separate straight chain hydrocarbons. There issues fromadsorber-desorber unit 51 via line 54 a finished light naphtha-reformatestream substantially free of straight chain hydrocarbons or having areduced straight chain hydrocarbon content. The desorbed straight chainhydrocarbons recovered from adsorber-desorber unit l via line 55 aresubjected to isomerization within isomerizer 60. Desirably thehydrogen-containing effluent recovered from gas separator 38 via line 39is employed as the desorbing medium to desorb the adsorbed straightchain hydrocarbons from the adsorbent within adsorber-desorber unit 51.When such a hydrogen-containing gaseous desorbing medium is employed theresulting desorbed straight chain hydrocarbons together with the gaseoushydrogen-containing desorbing medium is introduced directly intoisomerizer 6l) via lines 55 and 56. The isomerization reaction carriedout within isomerizer 60, preferably in the presence of aplatinum-containing catalyst so as to effect isomerization of thedesorbed straight chain hydrocarbons from adsorberesorber unit 5l,converts a substantial amount of the desorbed straight chainhydrocarbons into non-straight chain hydrocarbons which are removed fromisomerizer 6i) as isornate via line 6l. Advantageously the isomate isreturned to adsorber-desorber unit 51 to effect removal of the remainingunconverted straight chain hydrocarbons therefrom. As a result there isrecovered from adsorber-desorber unit 5l, as indicated in Fig. 2, aiinished light naphtha-reformate-isomate stream via line 54 having asubstantially reduced straight chain hydrocarbon content or a streamsubstantially free of straight chain hydrocarbons. The resultingfinished light naphtha-reforrnate-isomate stream from line 54 is blendedwith the heavy reformate stream in line 49 from fractionator 47 toproduce a nished blended product particularly suitable as a motor fuelin a spark ignition internal combustion type engine.

When the C4 gaseous eflluent recovered from debutanizer 4l via line 42introduced into adsorber-desorber unit 5l via line 62 is employed as thedesorbing medium the resulting desorbate which issues fromadsorber-desorber unit 51 via line 55 is desirably fractionated infractionator 64 for the separation and recovery of the C4 hydrocarbongaseous desorbing medium which is recovered from fractionator 64 vialine 65 for recycle via line 62 to adsorber-desorber unit 51 as gaseousdesorbing medium. After separation of the C4 and lighter hydrocarbonsthe remaining desorbate from fractionator 64 is introduced via line 66into isomerizer 60 to undergo isomerization, preferably in the presenceof gaseous hydrogen which advantageously is supplied from gas separator38 via lines 39 and 68. As indicated in Fig. 2, at least a portion ofthe C4 and lighter hydrocarbons separated from debutanizer 41 may beadded or otherwise blended via lines 42, 69 and 54 into the finishedblended product recovered vi-a line 49. Further, as indicated in Fig. 2,a portion of the C4 and lighter hydrocarbons recovered from debutanizer41 via line 42 may be added via lines 62 and 7@ to the gaseous hydrogenstream in line 39 in order to aid or better effect the desorption of theadsorbed straight chain hydrocarbons from the adsorbent withinadsorber-desorber unit Sl. As already mentioned, the gaseous hydrogenefuent from gas separator 38 is recycled at least in part to catalyticreforming unit 35 via lines 39 and 71.

If desired, although not specifically illustrated in Fig. 2, the heavynaphtha stream removed from fractionator 31 via line 34 may be contactedwith a selective adsorbent which selectively adsorbs straight chainhydrocarbons to the substantial exclusion of non-straight chainhydrocarbons to eect the removal of straight chain hydrocarbonstherefrom in the marmer described hereinabove prior to catalyticreforming, with the thus-separated straight chain hydrocarbons beingrecovered and isomerized in the manner indicated with respect to thestraight chain hydrocarbon desorbate issuing via line 55 from adsorbe-desorber unit 5l. An operation wherein a hy- S drocarbon stream isspecially treated to elfect the removal of straight chain hydrocarbonstherefrom prior to catalytic reforming is described in our copendingpatent application Serial No. 478,426 led December 29, 1954, thedisclosures of which are herein incorporated and made part of thisdisclosure.

Referring now to Fig. 3 of the drawing which schematically illustratesanother embodiment of the practice of this invention, a petroleumfraction containing straight chain hydrocarbons and non-straight chainhydrocarbons, such as a relatively wide boiling naphtha, eg., a straightrun naphtha having a boiling range in the range 60450 F., is introducedvia line into fractionator Sli from which there is removed overhead vialine 82 a depentanized light naphtha stream having a boiling range inthe range 75-275 F. From the lower end of fractionator 81 there isremoved via line 84 a heavy naphtha stream, such as a naphtha streamhaving a boiling range in the range ZOO-450 F.

The heavy naphtha stream in line 84 is introduced into catalyticreformer 85 wherein it undergoes catalytic reforming, involvingisomerization, dehydrogenation and aromatization or dehydrocyclization,all taking place more or less simultaneously.

There issues from catalytic reformer 85 via. line 86 a catalyticreformate which is introduced into gas separator 88 from which there isseparated overhead via line 89 a gaseous stream containing a largeproportion of or substantially only hydrogen. The remaining reformatestream from separator 88 is introduced via line 9i) into debutanizer orfractionator 9i from which there is removed overhead via line 92 anormally gaseous hydrocarbon stream containing C4 and lighterhydrocarbons. The remaining catalytic reformate is removed from thelower end of debutanizer 9i via line 94.

The catalytic reformate in line 94 is introduced into aromatichydrocarbon recover unit 95 wherein aromatic hydrocarbons are separatedtherefrom leaving recovery unit 95 via line 96. Aromatic recovery unit95 may comprise any suitable system involving solvent extraction,extractive distillation, adsorption, and the like, separately or incombination, for the separation of aromatic hydrocarbons fromnon-aromatic hydrocarbons. Suitable methods for the removal of aromatichydrocarbons from non-aromatic hydrocarbons include silica geladsorption, as exemplified by the Arosorb Process, solvent extractionwith a glycol such as diethylene glycol as exemplied by the UdexProcess, extractiva distillation by Contact with a liquid phenol streamor solvent extraction employing liquid furfural, liquid sulfur dioxide,liquid dimethylformarnide, Chlorex dicnloroethyl ether) and the like. Asuitable process for the recovery of aromatic hydrocarbons from acatalytic reformate is known as Rexforrning which involves the solventextraction of a catalytic reformate with a glycol solution for therecovery of high octane aromatic hydrocarbons as extract.

The resulting catalytic reformate now substantially free of aromatichydrocarbons or having a reduced aromatic hydrocarbon content isrecovered from aromatic recovery unit 95 via line 93 and introduced intoadsorber-desorber unit 99 wherein it contacts a selective adsorbent forthe adsorptive separation of straight chain hydrocarbons. There isremoved from adsorber-desorber unit 99 via line 100 a finished effluentstream comprised predominantly of non-straight chain non-aromatichydrocarbons. From adsorber-desorber unit 99 there is also recovered asa separate stream via line 10i an effluent stream cornprisedpredominantly of straight chain hydrocarbons. The efliuent stream ofstraight chain hydrocarbons in line lill is introduced into isomerizer02 where the straight chain hydrocarbons are aromatized or isomerized,preferably by means of a platinum-containing catalyst, to an isomatecomprising straight chain hydrocarbons and non-straight chainhydrocarbons which are recovered from isomerizer 102 via line ll04 andreturned va line 98 to adsorber-desorber unit 99 for the separation ofthe converted, non-straight chain hydrocarbons.

The light naphtha stream recovered overhead from fractionator 81 isintroduced via line 82 into adsorber- 85 via lines 125 and 84, therebyavoiding or bypassing the use of isomerizer 102.

Illustrative of the practice of this invention a mixture of straightchain hydrocarbons comparable to the mixdesorber unit 105 wherein itcontacts a solid selective 5 ture of straight chain hydrocarbonsrecovered as deadsorbent which selectively adsorbs Straight chainhysorbate from adsorber-desorber unit 51 of Fig. 2 and drocarbons to thesubstantial exclusion of non-straight adsorber-desorber units 99 and 105of Fig. 3 and comchain hydrocarbons. There is recovered fromadsorberprising 23% by vol. n-pentane, 56% by vol. n-hexane desorberunit 105 via line 106 a nished effluent Stream and 21% by vol. n-heptanewas contacted with a particlecomprised predominantly 0f light110D-Straight Chain hy- 10 form dehydrogenation-aromatization catalystcomprising drocarbons. There is also recovered from adsorber-CrZOa-MgO-Al203 at various temperatures and at a desorber unit 105 asdesorbate Via line 108 a Stream C0111- space velocity of about 0.4v./hr./V. at a pressure of PfSed predominantly 0f Straight ChainhydIO-l'bOIlS about 40 p\.s.i.g. and at a H2 recycle rate of 1200 cu.which are introduced into fractionator 109 for the sepaft/bb1 0f feed,The properties of the resulting up.. ration therefrom via line 110 ofthe gaseous desorbing 15 graded product are set forth in Table No. I.medium which may be a gaseous desorbing medium comprised predominantlyof hydrogen and introduced into Table N o' I adsorber-desorber unit 105from gas separator 88 via o l v lines 89 and 111. The separated straightchain hydroiiceaef:13:33: ""iiiiiiiiij: g stig carbon desorbate isrecovered from fractionator 109 via 20 BT01111116 0 2 line 112 andintroduced into isomerizer 114 where it is Xlfiireg; tccstffgffj 601g511g aromatized or isomerized, preferably in the presence of +3 C-TEL/ge1 80* 80-2 a platinum-containing catalyst and hydrogen gassupplied from gas separator 88 via lines 89, 115 and 112, to anLikewise, the same mixture of straight chain hydroisomate comprisingstraight chain hydrocarbons and noncarbons was contacted with a numberof platinum-constraight chain hydrocarbons. The resulting light isomatetaining reforming or predominantly isomerizing catalysts may berecovered from isomerizer 114 as product via at a pressure of about 500p.s.i.g., a H2 recycle rate of line 116. The light isomate, however, isalso advantaabout 4000 cu. ft./bbl. charge. The results are set forthgeously recovered from isomerizer 114 and recycled in Table No. II.

Table N0. II

Reaction Temp., F 800 850 900 Catalyst A B C A B C A B C P.D. Gas Make0. 209 0.178 0.150 0. 414 0. 338 0.299 2.567 2.609 0. 715

Liq. Rec., Wt. Percent. 95.9 99.3 90.1 95.0 99.0 88.2 67.6 70.1 72.7

isomate ASTM Res., C1ear.. 60.0 51.0 54.0 75.4 74.0 77.1 89.6 70.0 78.9

Finished (straight chain hydrocarbons removed) ASTM Res.,C1ear 78.0 61.072.0 84.0 82.0 82.6 80.3 Finished-l-S ce. TEL/gal 86.0

A-Platforming catalyst.

C-Ultraformng catalyst.

via lines 118 and 82 to adsorber-desorber unit 105 for the separation ofthe converted, non-straight chain hydrocarbons.

As indicated in Fig. 3 of the drawing, hydrogen is recycled frorn gasseparator 88 via lines 89 and 119 to catalytic reformer 85. Further, asindicated in Fig. 3, the C4 hydrocarbons stream recovered overhead fromfractionator 91 via line 92 are advantageously employed as the gaseousdesorbing medium within adsorber-desorber unit 105 being suppliedthereto via line 111. Further, as indicated in Fig. 3 of the drawing,the straight chain hydrocarbon desorbate may, if desired, be suppliedfrom adsorber-desorber unit 105 directly to catlytic reformer 85 vialines 108, 120 and 84. As is apparent from the foregoing operations,there is produced a iinal blended product via line 120 containing C4hydrocarbons recovered overhead from fractionator 91 via line 92,aromatic hydrocarbons recovered from aromatic recovery unit 95 via line96 and a non-straight chain non-aromatic hydrocarbon stream recoveredfrom adsorber-desorber unit 99 via line 100. If desired, the blendedproduct stream recovered via line 121 might also include the lightisomate recovered from isomerizer 114 via lines 116 and 122. Also, asindicated in Fig. 3, the blended productfin line 121 might also includethe light nonstraight'chain hydrocarbon fraction recovered fromadsorber-desorber unit 105 via lines 106 and 124. Further, asillustrated in Fig. 3, the straight chain hydrocarbon desorbaterecovered from adsorber-desorber 99 via line 101 may advantageously bereturned to catalytic reformer For purposes of simplicity and clarity,conventional control equipment, valves, pumps, compressors, heaters,coolers and supplementary gas-liquid, gas-solids and liquid-solidsseparators, fractionators, etc. have for the most part not beenillustrated in the drawings. The location and employment of theseauxiliary pieces of equipment such as may be necessary in the practiceof of this invention are well known to those skilled in the art.

As is evident to those skilled in the art many modiiications,substitutions and changes are possible in the practice of this inventionwithout departing from the spirit or scope thereof.

We claim:

1. A method of treating a petroleum fraction containing straight chainhydrocarbons and non-straight chain hydrocarbons which comprisesfractionating said fraction to produce a light naphtha having an endboiling point in the range -250 F. and a heavy naphtha having an endboiling point in the range 350-450 F., subjecting said heavy naphtha tocatalytic reforming with the resulting production of hydrogen, C5, C4and lighter hydrocarbons and a relatively wide boiling reformate,separating said hydrogen and said C4 hydrocarbons from said reformate,fractionating the remaining reformate into a light reformate having anend boiling point in the range 150-250 F. and a heavy reformate havingan end point in the range S50-450 F., introducing said light naphtha andsaid light reformate into contact with a selective solid adsorbent whichselectively adsorbs lll straight chain hydrocarbons to the substantialexclusion of non-straight chain hydrocarbons to remove straight chainhydrocarbons therefrom to yield a resulting treated lightnaphtha-reformate effluent, having a reduced straight chain hydrocarboncontent, desorbing the adsorbed straight chain hydrocarbons from saidadsorbent by contacting said adsorbent at an elevated temperature withsaid separated C4 hydrocarbons, separating from the resulting desorptionefuent the C4 hydrocarbons and the resulting desorbed straight chainhydrocarbons, introducing the resulting desorbed straight chainhydrocarbons into contact with an isomerization catalyst to isomerizesaid straight chain hydrocarbons, recovering from the isomerizationreaction an isomate, introducing said isomate into contact with aselective solid adsorbent material which selectively adsorbs straightchain hydrocarbons to the substantial exclusion of non-straight chainhydrocarbons to selectively remove straight chain hydrocarbons from saidisomate thereby yielding a resulting treated isomate having a reducedamount of straight chain hydrocarbons and blending the resulting treatedisomate, said treated light naphtha-reformate eluent and said heavyreformate to produce a petroleum product suitable as a motor fuel.

2. A method in accordance with claim l wherein said isomerizationreaction is carried out in the presence of said separated hydrogen.

3. A method in accordance with claim l wherein said light naphtha andsaid light reformate are introduced into contact with said selectivesolid adsorbent in an adsorption zone wherein said solid adsorbentmaterial moves downwardly and wherein the adsorbed straight chainhydrocarbons are desorbed from said adsorbent by contacting saidadsorbent within a vertically extending desorption zone under conditionssuch that straight chain hydrocarbons are desorbed from said adsorbentand simultaneously the solid adsorbent material is entrained and carriedalong upwardly within said desorption zone by said separated C4hydrocarbon employed as the gaseous desorbing medium.

4. A method of treating a petroleum fraction containing straight chainhydrocarbons and non-straight chain hydrocarbons which comprisesfractionating said fraction to produce a light naphtha having an endboiling point in the range G-250 F. and a heavy naphtha having an endboiling point in the range 350450 F., subjecting said heavy naphtha tocatalytic reforming with the resulting production of hydrogen, C4 andlighter hydrocarbons and a relatively wide boiling reformate, separatelyseparating said hydrogen and said C4 and lighter hydrocarbons from saidreformate, fractionating the remaining reformate into a light reformatehaving an end boiling point in the range 150-250 F. and a heavyreformate having an end point in the range 350450 F., introducing saidlight naphtha and said light reformate and isomate, produced as setforth hereinbelow, into contact with a selective solid adsorbent whichselectively adsorbs straight chain hydrocarbons to the substantialexclusion of non-straight chain hydrocarbons to remove the straightchain hydrocarbons therefrom to yield a resulting treated lightnaphtha-reformate-isomate eiuent, desorbing the adsorbed straight chainhydrocarbons from said adsorbent by contacting said adsorbent at anelevated temperature with said separated hydrogen, introducing theresulting desorbed straight chain hydrocarbons together with saidhydrogen into contact with an isomerization catalyst to isomerize saidstraight chain hydrocarbons, recovering from the isomerization reactionsaid isomate and blending the resulting treated lightnaphtha-reformate-isomate effluent with said heavy reformate to producea petroleum product suitable as a motor fuel.

5. A method of treating a petroleum fraction containing straight chainhydrocarbons and non-straight chain hydrocarbons which comprisesfractionating said naphtha to produce a light naphtha having an endboiling point in the range 15G-250 F. and a heavy naphtha having an endpoint in the range 350-450" F., subjecting said heavy naphtha tocatalytic reforming with the resulting production of hydrogen, C4 andlighter hydrocarbons and a relatively wide boiling reformate, separatelyseparating said hydrogen, said C4 and lighter hydrocarbons and saidreformate, fractionating said reformate into a light reformate having anend boiling point in the range l5()- 250 F. and a heavy reformate havingan end point in the range S50-450 F., introducing said light naphtha,said light reformate and an isomate, produced as described hereinbelow,into contact with a selective solid adsorbent which selectively adsorbsstraight chain hydrocarbons to the substantial exclusion of non-straightchain hydrocarbons to remove straight chain hydrocarbons therefrom toyield a resulting treated light naphthareformate-isomate eiuent,desorbing the adsorbed straight chain hydrocarbons from said adsorbentby contacting said adsorbent with said separated C4 hydrocarbon stream,separating from the resulting desorption effluent C4 hydrocarbons andthe resulting desorbed straight chain hydrocarbons, introducing theresulting desorbed straight chain hydrocarbons into contact with anisomerization catalyst in the presence of said separated hydrogen toisomerize said straight chain hydrocarbons, recovering from theisomerization reaction said isomate, and blending the resulting treatedlight naphtha-reformate-isomate effluent with said heavy reformate toproduce a petroleum product suitable as a motor fuel.

6. A method in accordance with claim 5 wherein a portion of saidseparately separated C4 hydrocarbon is blended with said petroleumproduct.

7. A method of treating a petroleum fraction containing straight chainhydrocarbons and non-straight chain hydrocarbons which comprisesfractionating said fraction to produce a light naphtha having an endpoint in the range 15G-250 F. and a heavy naphtha having an end point inthe range 350450 F., subjecting said heavy naphtha to catalyticreforming with the resulting production of hydrogen, C4 hydrocarbons anda reformate containing aromatic hydrocarbons, separating said hydrogenand said C4 hydrocarbons from said reformate, treating the remainingreformate to separate therefrom a separate stream comprising saidaromatic hydrocarbons, introducing the resulting reformate stream nowhaving a reduced aromatic hydrocarbon content into contact with aselective solid adsorbent which selectively adsorbs straight chainhydrocarbons to the substantial exclusion of non-staright chainhydrocarbons to remove straight chain hydrocarbons therefrom to yield atreated reformate having a reduced straight chain hydrocarbon contentand comprised predominantly of non-straight chain, non-aromatichydrocarbons, desorbing the adsorbed straight chain hydrocarbons fromsaid adsorbent, isomerizing the desorbed straight chain hydrocarbons toproduce an isomate containing straight chain hydrocarbons andnon-straight chain hydrocarbons, contacting said isomate with said solidadsorbent to separate straight chain hydrocarbons therefrom to yield atreated isomate having a reduced amount of straight chain hydrocarbons,isomerizing the aforesaid separated light naphtha, and blending saidseparated C4 hydrocarbons, said aromatic hydrocarbons, said treatedisomate, the resulting isomerized light naphtha and said non-straightchain, non-aromatic hydrocarbons to produce a blended product having animproved quality as a motor fuel for spark ignition internal combustionengines.

8. A method of treating a petroleum fraction containing straight chainhydrocarbons and non-straight chain hydrocarbons which comprisesfractionating said fraction to produce a light naphtha having an endpoint in the range 15C-250 F. and a heavy naphtha having an end point inthe range E60-450 F., subjecting said heavy naphtha to catalyticreforming with the resulting production of hydrogen, C4 hydrocarbons anda reformate containing aromatic hydrocarbons, separating said hydrogenand said C4 hydrocarbons from said reformate, treating the remainingreformate to separate therefrom a separate stream comprising aromatichydrocarbons, introducing the resulting reformate stream now having areduced aromatic hydrocarbon content into contact with a selective solidadsorbent which selectively adsorbs straight chain hydrocarbons to thesubstantial exclusion of non-straight chain hydrocarbons to removestraight chain hydrocarbons therefrom to yield a treated reformatehaving a reduced straight chain hydrocarbon content and comprisedpredominantly of non-straight chain, nonaromatic hydrocarbons, desorbingthe adsorbed straight chain hydrocarbons from said adsorbent,isomerizing the desorbed straight chain hydrocarbons to produce anisomate containing straight chain hydrocarbons and nonstraight chainhydrocarbons, contacting said isomate with said solid adsorbent toseparate straight chain hydrocarbons therefrom and to yield a treatedisomate having a reduced amount of straight chain hydrocarbons, blendingsaid separated C4 hydrocarbons, said aromatic hydrocarbons, said treatedisomate and said non-straight chain, non-aromatic hydrocarbons toproduce a blended product having an improved quality as a motor fuel forspark ignition internal combustion engines, contacting the aforesaidlight naphtha with a solid selective adsorbent which selectively adsorbsstraight chain hydrocarbons to the substantial exclusion of non-straightchain hydrocarbons to remove straight chain hydrocarbons therefrom toyield a treated light naphtha having a reduced straight chainhydrocarbon content, separating said treated light naphtha, adding saidtreated light naphtha to said blended product, desorbing the adsorbedstraight chain hydrocarbons derived from said light naphtha from saidadsorbent, isomerizing the resulting desorbed straight chainhydrocarbons to produce a corresponding isomate containing straightchain hydrocarbons and non-straight chain hydrocarbons and adding saidcorresponding isomate to the aforesaid blended product.

9. A method of treating a petroleum fraction containing straight chainhydrocarbons and non-straight chain hydrocarbons which comprisesfractionating said fraction to produce a light naphtha having an endpoint in the range 15G-250 F. and a heavy naphtha having an end point inthe range 350-450 F., subjecting said heavy naphtha to catalyticreforming with the resulting production of hydrogen, C4 hydrocarbons anda reformate containing aromatic hydrocarbons, separating said hydrogenand said C4 hydrocarbons from said reformate, treating the remainingreformate to separate therefrom a separate stream comprising saidaromatic hydrocarbons, introducing the resulting reformate stream nowhaving a reduced aromatic hydrocarbon content into contact with aselective solid adsorbent which selectively adsorbs straight chainhydrocarbons to the substantial exclusion of nonstraight chainhydrocarbons to remove straight chain hydrocarbons therefrom to yield atreated reformate having a reduced straight chain hydrocarbon contentand comprised predominantly of non-straight chain, non-aromatic '14hydrocarbons, desorbing the adsorbed straight chain hydrocarbons fromsaid adsorbent, isomerizing the desorbed straight chain hydrocarbons toproduce an isomate containing straight chain hydrocarbons andnon-straight chain hydrocarbons, contacting said isomate with said solidadsorbent to separate straight chain hydrocarbons therefrom, blendingsaid separated C4 hydrocarbons, said aromatic hydrocarbons and saidnon-straight chain, non-aromatic hydrocarbons to produce a blendedproduct having animproved quality as a motor fuel for spark ignitioninternal combustion engines, contacting the aforesaid light naphtha witha solid selective adsorbent which selectively adsorbs straight chainhydrocarbons to the substantial exclusion of non-straight chainhydrocarbons to remove straight chain hydrocarbons therefrom to yield atreated light naphtha having a reduced straight chain hydrocarboncontent, separating said treated light naphtha, adding said treatedlight naphtha to said blended product, desorbing the adsorbed straightchain hydrocarbons derived from said light naphtha from said adsorbent,isomerizing the resulting desorbed straight chain hydrocarbons toproduce a corresponding isomate containing straight chain hydrocarbonsand non-straight chain hydrocarbons, contacting said correspondingisomate with said solid adsorbent to separate straight chainhydrocarbons therefrom to produce a treated corresponding isomate havinga reduced straight chain hydrocarbon content and adding said treatedcorresponding isomate to said blended product.

l0. A method of treating a petroleum fraction containing straight chainhydrocarbons and non-straight chain hydrocarbons in accordance withclaim 7 wherein said separated hydrogen is present during the operationwherein said desorbed straight chain hydrocarbons are isomerized toproduce an isomate containing straight chain hydrocarbons andnon-straight chain hydrocarbons.

11. A method of treating a petroleum fraction containing straight chainhydrocarbons and non-straight chain hydrocarbons in accordance withclaim 7 wherein said separated hydrogen is employed to desorb theadsorbed straight chain hydrocarbons from said adsorbent and whereinsaid separated hydrogen is present during the isomerizing operationwherein the resulting desorbed straight chain hydrocarbons areisomerized to produce an isomate containing straight chain hydrocarbonsand nonstraight chain hydrocarbons.

References Cited in the file of this patent UNITED STATES PATENTS2,425,535 Hibshman Aug. 12, 1947 2,495,842 Gilliland Ian. 31, 19502,522,426 Black Sept. 12, 1950 2,552,436 Bennett et al May 8, 19512,651,597 Corner et al Sept. 8, 2953 2,697,684 Hemminger et al Dec. 21,1954 2,801,966 Mertes et al Aug. 6, 1957 2,818,449 Christensen et al.Dec. 31, 1957

1. A METHOD OF TREATING A PETROLEUM FRACTION CONTAINING STRAIGHT CHAINHYDROCARBONS AND NON-STRAIGHT CHAIN HYDROBONS WHICH COMPRISESFRACTIONATING SAID FRACTION TO PRODUCE A LIGHT NAPHTHA HAVING AN ENDLOILING POINT IN THE RANGE 150-250* F. AND A HEAVY NAPHA HAVING AN ENDBOILING POINT IN THE RANGE 350-450* F., SUBJECTING SAID HEAVY NAPHTHA TOCATALYTIC REFORMING WITH THE RESULTING PRODUCTION OF HYDROGEN, C5 C4 ANDLIGHTER HYDROCARBONS AND A RELATIVELY WIDE BOILING REFORMATE, SEPARATINGSAID HYDROGEN AND SAID C4 HYDROCARBONS FROM SAID REFORMATE,FRACTIONATING THE REMAINING REFORMATE INTO A LIGHT REFORMATE HAVING ANEND BOILING POINT IN THE RANGE 150-250* F. AND A HEAVY REFORMATE HAVINGAN END POINT IN THE RANGE 350-450* F., INTRODUCING SAID LIGHT NAPHTHAAND SAID LIGHT REFORMATE INTO CONTACT WITH A SELECTIVE SOLID ADSORBENTWHICH SELECTIVELY ADSORBS STRAIGHT CHAIN HYDROCARBONS TO THE SUBSTANTIALEXCLUSION OF NON-STRAIGHT CHAIN HYDROCARBONS TO REMOVE STRAIGHT CHAINHYDROCARBONS THEREFROM TO YIELD A RESULTING TREATED LIGHTNAPHTHA-REFORMATE EFFLUENT, HAVING A REDUCED STRAIGHT CHAIN HYDROCARBONCONTENT, DESORBING THE ADSORBED STRAIGHT CHAIN HYDROCARBONS FROM SAIDADSORBENT BY CONTACTING SAID ADSORBENT AT AN ELEVATED TEMPERATURE WITHSAID SEPARATED C4 HYDROCABON SEPARATING FROM THE RESULTING DESORPTIONEFFLUENT THE C4 HYDROCARBONS AND THE RESULTING DESORBED STRAIGHT CHAINHYDROCARBONS, INTRODUCING THE RESULTING DESORBED STRAIGHT CHAINHYDROCARBONS INTO CONTACT WITH AN ISOMERIZATION CATALYST TO ISOMERIZESAID STRAIGHT CHAIN HYDROCARBONS, RECOVERING FROM THE ISOMERIZATIONREACTION AN ISOMATE, INTRIDUCING SAID ISOMATE INTO CONTACT WITH ASELECTIVE SOLID ABSORBENT MATERIAL WHICH SELECTIVELY ADSORBS STRAIGHTCHAIN HYDROCARBONS TO THE SUBSTANTIAL EXCLUSION OF NON-STRAIGHT CHAINHYDROCARBONS TO SELECTIVELY REMOVE STRAIGHT CHAIN HYDROCARBONS FROM SAIDISOMATE THEREBY YIELDING A RESULTING TREATED ISOMATE HAVING A REDUCEDAMOUNT OF STRAIGHT CHAIN HYDROCARBONS AND BLENDING THE RESULTING TREATEDISOMATE, SAID TREATED LIGHT NAPHTHA-REFORMATE EFFLUENT AND SAID HEAVYREFORMATE TO PRODUCE A PETROLEUM PRODUCT SUITABLE AS A MOTOR FUEL